FWIW the associated crime wave was much broader than carjacking (and I’m actually not aware of a particular increase in carjackings specifically due to the Kia issues but I don’t know) but the Kia issues seem to have started in Milwaukee.

For whatever reason, it became A Thing here more than a year before it went national. Car thefts in Milwaukee more than doubled (entirely due to a stupidly large increase in Kia/Hyundai thefts) and we got a reputation for Kia thefts before it became a national issue